Design Evaluation of Multiroll Mills for Small-diameter wire rolling - PowerPoint PPT Presentation

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Design Evaluation of Multiroll Mills for Small-diameter wire rolling

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A round rod is used as a starting place for the ensuing rolling reductions. ... Mother wire to come from smallest available hot-rolled rod on the market. 5 or 6 mm ... – PowerPoint PPT presentation

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Title: Design Evaluation of Multiroll Mills for Small-diameter wire rolling


1
Design Evaluation of Multiroll Mills for
Small-diameter wire rolling
  • Paper by K. Kuroda, T. Kuboki, Y. Imamura

Presentation by Adam Slade Monday, 17 September,
2007
2
Background
  • Wire rolling is being utilized rather than the
    more traditional wire drawing method of
    production. A round rod is used as a starting
    place for the ensuing rolling reductions.

3
Purpose of the Paper
  • Demonstrate differences in forces and
    advantages/disadvantages of wire rolling using
    different numbers of rollers
  • Show wire rolling to be a good alternative to
    wire drawing, specifically wire rolling with
    multiple rollers

4
Why?
  • Conversion from drawing to rolling ensures a
    high reduction in area per pass, because the
    severe sliding frictional condition is almost
    eliminated.
  • The Reality most of the contact area of the
    rollers with the wire involves sliding friction,
    and no data is provided as a comparison between
    the two methods

5
Comparison to Previous Work
  • Many papers/studies had been previously been made
    examining the advantages and disadvantages of
    multiple rolls in wire manufacture
  • Authors angle none of the previous studies
    has compared the deformation and loading
    characteristics of the three mills on an even
    basis, i.e. on the same roll and groove geometry
    design basis, and direct one-to-one comparisons
    have not been made of all three mills on a
    numerical and experimental basis.

6
Authors Possible Motive
  • Such study may enable further development of the
    multiroll cold wire rolling mill in the next
    decade.
  • The authors created a four-roll micromill named
    the super-micromill

7
Objectives in Design
  • There was to be no tension in the wire between
    stands (as opposed to the drawing method)
  • Driving torque given from one source to all
    stands through a common drive (one motor)
  • Compact design

8
Limitations of Experimentation
  • Only to examine 2, 3 and 4 roll stands
  • Stand composed of more than five rolls is not
    realistic because of complexity
  • Why a 5 roll stand is not examined

9
The Setup
  • 2 roll unit driven by two shafts
  • 3 and 4 roll unit driven by single shaft
  • Roll force measured using load cell
  • Driving torque calculated by revolution rate and
    power consumption

10
(No Transcript)
11
Specifications for prototype mill
Authors offer no explanation for calculation of
nominal roll diameter, or rolling speed
12
Obtaining Results
  • Contact Area with rollers

13
Comparing the Model to the Data
  • Conclusion Why bother with any further actual
    experimentation?

14
Considerations for further models
  • Mother wire to come from smallest available
    hot-rolled rod on the market
  • 5 or 6 mm
  • Minimum diameter wire taken as the smallest wire
    in the world
  • The authors report it to be 1.2 mm
  • Minimum diameter produced from first source
    investigated found to be 0.14 mm for Cu, 0.25 mm
    for aluminum, 0.38 mm for carbon steel
  • Reference obtained from the authors own previous
    paper
  • Roll diameter comes from accepted market data
  • Minimum ratio of roll diameter to wire diameter
    is 20
  • Maximum roll size based on the following
    statement
  • It is known that, the larger the roll shaft and
    the machine size, the larger is the bearing load
    but the higher the machine cost.

15
(No Transcript)
16
Finite Element Analysis
  • CORMILL finite element code developed by the
    University of Tokyo
  • For three-dimensional rigid-plastic steady
    state analysis of rolling
  • Performed over one-half of the contact area with
    each roller

17
Results
  • As the reduction in area increases, ovality
    increases
  • This tendency becomes greater as the ratio of
    roll diameter to wire diameter increases

18
Manipulation of Results
  • Over-emphasis on ovality favors the 4-roll
    configuration. Ovality the only consideration in
    precision.
  • the four-roll mill is most advantageous in
    ensuring precision when subjected to
    smaller-diameter wire rolling.

19
Comparison of Results
  • It has been said that, the smaller the number of
    rolls, the higher the reduction becomes, i.e.
    better performance can be obtained in the order
    two-rollgtthree-rollgtfour-roll. but
  • This paper compares the performance given equal
    dimensional tolerances, on unequal measuring
    techniques.

20
Loading Results
  • the two-roll mill requires greater torque than
    either the three- or four-roll mills.
  • Total rolling force is equivalent for all
    rollers, indicating the same power requirement
    for each configuration

21
Torque inequalities
  • The three different configurations require
    different torque requirements. Not an even
    comparison.
  • Assumption of constant frictional work on each
    roller likely false, due to different contact
    areas/deformations.

22
Force vs. Torque
  • Rolling force is approximately equal
  • Power requirement based on force, not torque
  • Lower portion shows the inequalities in the setup
    of equipment

23
Calculations based on
  • Three data points enough?

24
More Unfair Comparisons
  • Measuring rolling force per one roll
  • Not linear as shown
  • Isnt it obvious that the rolling force per roll
    should decrease this drastically for an increased
    number of total rolls?
  • Red lines indicate the 2- and 3-roll positions
    normalized (as if all rollers had four members)
  • the three-roll actually has the lowest total
    rolling force

25
Conclusion Disadvantages and Considerations
  • Prolonged manufacture time, due to greater
    restrictions on reduction ratio
  • More complex machinery twice as many rollers
    twice as much maintenance
  • Other effects on the final product not considered
    (additional work hardening, heat introduced into
    machinery due to greater deformations, etc.)

26
Conclusion Advantages and Implications
  • The four-roll micomill would provide a good way
    to create high tolerance small diameter wire for
    a lower energy requirement over drawing, and a
    very slightly lower energy requirement over a
    two-roll mill
  • This improve the efficiency of the wire industry
    greatly, if high tolerances are more desirable
    than the increase in equipment and increase in
    processing time

27
References
  • Four of the sources are the authors own work,
    all but four are from Japan (presumably written
    by coworkers), and those four are from 1983,
    1983, 1982, and 1952
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